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Anti-proton and positron Galactic cosmic ray spectra are among the keytargets for indirect detection of dark matter. The boost factors, correspondingto an enhancement of the signal and linked to the clumpiness properties of thedark matter distribution, have been taken as high as thousands in the past. Thedramatic impact of these boost factors for indirect detection of antiparticles,for instance with the PAMELA satellite or the coming AMS-02 experiment, asksfor their detailed calculation. We take into account the results of highresolution N-body dark matter simulations to calculate the most likely energydependent boost factors linked to the cosmic ray propagation properties, foranti-protons and positrons. Starting from the mass and space distributions ofsub-halos, the anti-proton and positron propagators are used to calculate themean value and the variance of the boost factor for the primary fluxes. We takeadvantage of the statistical method introduced in Lavalle et al. (2007) andcross-check the results with Monte Carlo computations. By spanning some extremeconfigurations of sub-halo and propagation properties, we find that the averagecontribution of the clumps is negligible compared to that of the smooth darkmatter component. Sub-halos do not lead to enhancement of the signals, unlessthey are taken with some extreme (unexpected) properties. This result isindependent of the nature of the self-annihilating dark matter candidateconsidered, and provides precise estimates of the theoretical and thestatistical uncertainties of the antimatter flux from dark mattersubstructures. Spectral distortions can still be expected in antimatter fluxmeasurements, but scenarios invoking large and even mild clumpiness boostfactors are strongly disfavoured by our analysis.

Full calculation of clumpiness boost factors for antimatter cosmic rays in the light of Lambda-CDM N-body simulation results